Genetics and lifestyle factors are major determinants of bone density and ultimately the risk for developing osteoporosis. Higher bone density was reported in rural vs. urban adolescents. We recently reported high bone density Z scores among female members of the Hutterite Brethren, a religious group living a rural communal lifestyle. We concluded that high levels of physical activity beginning in the teen years in the presence of adequate calcium intake over a lifetime might result in increased bone gain and subsequent above normal adult bone density. However, it is not known whether Hutterites have higher bone density than other populations living similar lifestyles, or whether the higher bone density among older Hutterites is due to a slower rate of later bone loss. The aim of this study is determine whether a rural lifestyle is conducive to optimizing peak bone mass in young adulthood and minimizing rates of later bone loss, thereby explaining the high bone density among the rural Hutterite population. The proposed aim will be addressed with a three-year longitudinal study of 1,164 men and women aged 20 to 65 years with equal numbers of Hutterites, rural non-Hutterites, and non-rural non- Hutterites. We will obtain yearly bone measurements and quarterly assessments of activity levels and dietary intake. The project will determine whether bone density during young adulthood and the rate of later bone loss, among the Hutterites is similar to other populations, and whether greater activity levels and calcium intake can account for the high bone density observed among the Hutterites. Further understanding of the role of lifestyle factors as determinants of bone density among Hutterites is necessary because they appear to be significantly less susceptible to the development of osteoporosis than the normal U.S. population.